A seller can place in the amount that each bid increases by following each bid.

An example :
The seller starts a auction as below:

$ 1.00 Start price
$ 5.00 Increase-amount

Then, the bids follow in steps like below:

$ 1.00
$ 6.00
$ 12.00
$ 18.00
$ 24.00
$ 30.00
$ 36.00
etc.